JPS5819629B2 - Corrosion resistant hard alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hard alloy with excellent corrosion resistance.

Conventionally, WC-TiC cemented carbide has been used for mechanical seals and other applications, and its typical composition is TiC.
The remaining WC was around quintuple chordates.

However, recently there has been a demand for superior strength and corrosion resistance, and the situation has come such that the above-mentioned WC-Tic system is no longer satisfactory.

The present invention is to improve sinterability and provide an alloy with high crack resistance by incorporating an appropriate amount of TiN into this WC-TiC cemented carbide. %, titanium nitride in an amount of 1 to 3% by weight, and the balance being tungsten carbide.

In addition, most of the above are written as titanium carbide, titanium nitride, and tungsten carbide, and not Tic, TiN, and WC, but most of them are Tic, TiN, and WC, but since commercially available raw materials were used for each, bonded carbon It is conceivable that some types have a little more or less bonded nitrogen, but there is no problem with such things, and these will be referred to as TiC below.

Represented by TiN and WC.

An example of the experiment that led to the development of the alloy of the present invention and its results is shown below.

In this experiment, the raw materials were TiC (total carbon content 20.03% by weight) and TiC (total carbon content 20.03% by weight) with an average particle diameter of 10 to 1.5 μm, total carbon content of 615 to 6.25, weight class WC1, and average particle diameter of 1 to 3 μm. A suitable amount of N (total nitrogen content: 21% by weight) was blended and mixed in a ball mill for 48 hours using acetone as a solvent. After molding, pre-sintering at 800°C followed by 16
The composition and physical property values of the samples obtained by main sintering at 80° C. for 60 minutes are shown in Table 1 below.

The porosity, crack resistance and corrosion resistance tests for the samples having the compositions shown in Table 1 above are shown in Table 2 below.

In Table 2 above, "porosity" is based on the porosity classification standard for cemented carbide of Cl5OO6" 1966.

In addition, "crack resistance" is the sum of the four values obtained by making an indentation on a sample using the "Vickers hardness test method" using a load of 30 kg, and measuring the cracks that occur in the squares under a microscope with a magnification of 130. is 30 kg/Σ, l, [ky/mm ] when ΣL is taken as ΣL.

In addition, "corrosion resistance test results" are HCt, H2SO4, NaOH
The graph shows the weight loss per unit surface area after being immersed in each 10% solution for 24 hours at a liquid temperature of 50°C.

Furthermore, 200 times magnification micrographs of the uncorroded lap surfaces of samples A3 and A6 used to examine the above-mentioned porosity are shown in FIGS. 1 and 2, respectively.

As mentioned above, the alloy composition of the present invention containing TiN has a
It can be seen that as a result of the improved sinterability, the relative density tends to be smaller and the crack resistance is improved.

However, when TiN<1, the porosity is poor and the relative density does not increase; on the other hand, as shown in sample A7,
When iN>3, the porosity also tends to deteriorate.

Furthermore, as seen in sample shop 6, it was confirmed that corrosion resistance deteriorates when T i N < 1.

As described above, the alloy of the present invention is hard, has good crack resistance, and has good corrosion resistance, so it is excellent as a material for chemical-related valves and nozzles, including rings for mechanical seals.

[Brief explanation of drawings]

FIGS. 1 and 2 show micrographs of the corrosion-free lap surfaces of sample plates 3 and 6, respectively, both at a magnification of 200x.

Claims (1)

[Claims] 1 A corrosion-resistant hard alloy consisting of 2 to 5% by weight of titanium carbide, 1 to 3% by weight of titanium nitride, and the balance tungsten carbide.